A box contains 15 green and 10 yellow balls.

Question

A box contains 15 green and 10 yellow balls. If 10 balls are randomly drawn, one-by-one, with
replacement, then the variance of the number of green balls drawn is :

Accepted Answer

We can apply binomial probability distribution

n = 10

p = Probability of drawing a green ball = $${{15} \over {25}}$$ = $${3 \over 5}$$

Also q = 1 - $${3 \over 5}$$ = $${2 \over 5}$$

Variance = npq

= $$10 \times {3 \over 5} \times {2 \over 5}$$ = $${{12} \over 5}$$

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